AN4243

Designing an application with the L6230

Doc ID 024199 Rev 1

13/29

Figure 9.

Obtaining a reference voltage through a PWM output of microcontroller

Assuming that this output swings from 0 to 5V, the resulting average voltage is:

Equation 10

where DµC is the duty cycle of the PWM output of the microcontroller.

Assuming that the microcontroller output impedance is lower than 1 k

more time to vary after changing the duty cycle of the microcontroller PWM. Besides, too

a poor noise immunity.

As sensing resistor value is typically kept small, a small noise on CP- input pins might cause

a considerable error in the output current. It is then recommended to decouple this pin with a

ceramic capacitor of some tens of nF, placed very close to CP- and GND pins.

Note that CP- pin connected to GND cannot guarantee zero current due to voltage offset in

the internal comparator. The best way to cut down the IC power consumption and to clear

the load current is to pull down the DIAG/EN pin.

With very small reference voltage, PWM current control method can lose control of the

current due to the minimum allowed duration of on-time.

P

C

P

C

CP-

GND

PWM Output

of a µC

AM16571v1

V

CP-

5V

⋅⋅

R

CP1

R

CP2

+

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=